Catheters for medical diagnostic or therapeutic use are well known. A catheter has a distal end and a proximal end, with a body extending therebetween and a lumen extending therethrough from end to end. A wide variety of catheters exists for percutaneous insertion by the Seldinger technique into the vascular system to accomplish diagnostic or therapeutic objectives. The vessels of the peripheral vasculature have a relatively large diameter and low tortuosity, the coronary vasculature is somewhat smaller and more tortuous, and the vasculature in the soft tissue of the brain and liver is of small lumen and is very tortuous.
In order to be able to access the various parts of the vasculature, the catheter needs to be flexible and to maintain its column strength when it follows a tortuous path. The contradictory requirements for flexibility and column strength are particularly pronounced in catheters for intracranial catheterizations used in a variety of diagnostic and interventional neurological techniques including delivery of contrast fluids, drugs or a vasoocclusive agent, treatment of tumors, aneurysms, AVS (arteriovenous shunts) and so forth.
When a central member is to be moved within a catheter or sheath to perform an activity at or beyond the distal end of the catheter, after the catheter has been positioned, the central member is to be pushed through the catheter lumen. The more tortuous the path and the smaller the catheter the more difficult it is to advance the central member through the catheter lumen. This difficulty is in particular pronounced in coaxial systems for intracranial use. Where the central member is a delivery device for an embolization coil and must be rotated to disconnect from the coil upon release at the treatment site, the central member must be capable of transmitting torque to its distal end for assured coil disconnection; one such prior art coil delivery system is disclosed in U.S. Pat. No. 5,122,136; but it is a common problem that such prior art coil delivery members have relatively high rigidity which is problematic in small or tortuous vessels with aneurysms. Where the device is a pusher to push a device such as a stent from the distal end of the catheter, the pusher must have substantial column strength as well as great flexibility.
Where a catheter is to be used for delivery of an endovascular prosthesis to a treatment site, such as a stent, a stent graft, a valve member, or a filter, where the prosthesis is compressed to pass through the catheter and then selfexpand upon release therefrom within a body lumen, the prosthesis must be constrained while within the catheter and imposes significant forces against the surrounding catheter body.
It is an objective of the present invention to provide a medical device that includes a distal area that is very flexible and yet easily pushable and capable of transferring torque in an assured, controllable manner.
It is another objective to provide a catheter system that makes it easier to advance the central member through the catheter also in cases where the catheter exhibits sharp turns.
It is further an objective to provide a catheter that resists the substantial radially outward forces of a compressed endovascular prosthesis contained within the distal end thereof, and yet be very flexible and capable of transferring torque.
It is yet another objective to provide a central member for movement within a catheter lumen that is very flexible, has substantial column strength and/or is capable of transferring torque.